Conventional receiver systems typically down covert received signal frequencies to intermediate frequencies for signal processing purposes. Some receiver systems that receive signal frequencies over a wide range require very large intermediate frequency bandwidths. For example, in some sub-millimeter wave spectroscopy systems the intermediate frequency can vary over hundreds of gigahertz. Increasing the bandwidth of the intermediate frequency stages to handle all possible incoming signals may decrease the signal-to-noise ratio of the receiver system. Conventional approaches to keeping a constant intermediate frequency with a minimum bandwidth are limited for a variety of reasons.